The body is a universe of cells and activity

Relaxing, are you? Actually, you're not. You may be pushed back in your favorite Sunday morning easy chair, but whether you know it or not you are engaged in a desperate, exhausting fight for your life. Don't take my word for it. Do the numbers.

Your body consists of 100,000,000,000,000 cells, give or take. That's a pretty meaningless number unless you're an astronomer, so let's put it in more immediate terms. If each of your body's cells were the size of a ping-pong ball, that number of ping-pong ball-size cells would fill up more than 1,000 Empire State buildings. Let's agree that's a lot of cells.

More amazingly, each of those cells contains about 3 feet of DNA, the genetic material that directs inheritance and all the functions of each cell. It may seem ridiculous that a microscopic cell could contain 3 feet of DNA. If, again, you scaled a cell up to the size of a ping-pong ball, its DNA would now be the equivalent of a quarter of a mile long. How do you stuff a quarter mile of DNA into a ping-pong ball?

With great care.

DNA has the shape of a very, very thin rope ladder, the rungs of which form your DNA sequence. However, that ladder is twisted (the so-called double helix), then coiled, recoiled, and recoiled very precisely several more times to fit into a cell. The 3 feet of DNA per cell is what you get if you completely uncoil it all and lay the pieces end-to-end. If you did this for all the DNA in all cells of your body, your DNA as you sit there blithely reading your newspaper would stretch out beyond the moon, beyond the sun, beyond Mars and Jupiter. It fact, it would stretch past Pluto to the limits of our solar system and back again — several times. Impressed by yourself yet?

So how does this translate into the exhausting desperate fight for life I mentioned? Even though you may be just sitting there, your cells aren't. Each is a busy miniature factory, constantly churning out new proteins and hormones, kick-starting thousands of chemical reactions, storing nutrients, doing all the things that cells have to do to keep you alive. But the factories are under assault. They are continually attacked by the equivalent of hammer-wielding vandals pounding randomly on the machinery. We call these vandals free radicals, which are produced by the cells themselves. But there are other vandals too. Thanks to these vandals, the DNA in each one of your cells is damaged more than 10 thousand times per day. I'll leave the calculations of the total damage to you. It's more than astronomical, but remarkably almost all of it will be repaired. That repair, too, takes energy.

Replacing entire cells takes even more energy. Cells are routinely shed from your skin and the inside of the many, many miles of tubes and vessels in your body. Cells also die when they are too damaged to repair themselves. Dead and shed cells must be replaced, which requires the manufacture of new DNA, new proteins, new everything in a cell.

If your mind is still unboggled, consider this: Just to keep pace with damage to — and regular loss of — your cells, you need to produce about 25 million new cells per second. Yes, I said “per second.” To do this, you need to manufacture about 14,000 miles of new DNA each and every second of your life. What's more, during that second, the new 14,000 miles of DNA you just made will be damaged more than 10 million times. Don't worry. You will repair it.

It might explain why you feel so exhausted on an otherwise pleasant Sunday morning, however.